In general, a main transmitter and repeaters are deployed in service coverage according to surrounding natural features/objects. Repeaters are disposed in an area where signals from a main transmitter are received weak, which is called a weak signal reception area, to resolve unstable signal reception and broaden a signal transmission area, or coverage, of the main transmitter.
FIG. 1 illustrates an example of a service employing conventional repeaters. The drawing shows how repeaters repeat signals using different frequencies.
Referring to FIG. 1, in the service using conventional repeaters, signals are transmitted from a main transmitter 101 through transmission frequency A, and repeaters 102 to 105 repeats the signals using frequencies B, C, D and E that are different from the transmission frequency A. However, the repeaters illustrated in FIG. 1 resolve unstable signal reception in a weak signal reception area and broaden the signal transmission coverage, using the different frequencies B, C, D and E for the respective repeaters. The repeaters 102 to 105 use a plurality of frequency bands, and this is inefficient from the perspective of frequency utility because it requires much frequency resources.
If a broadcasting service is provided and a plurality of repeaters use the same frequency band as the main transmitter does, the frequency utility efficiency will be highly efficient because the frequency is reused in neighboring area.
FIG. 2 illustrates another example of a service employing conventional repeaters. The drawing shows a service using on-channel repeaters repeating signals through the same frequency.
To be specific, a main transmitter 201 transmits signals through a transmission frequency A, and on-channel repeaters 202 to 205 repeat the signals in the same frequency as the transmission frequency A. The service using on-channel repeaters, however, requires high isolation between a transmission antenna and a reception antenna. Thus, there are restraints that it can hardly use existing signal transmission facility and that it requires high capital investment.
Meanwhile, distributed repeaters (DTxR) can build up a distributed repeat network in a short time, maximally utilizing existing signal transmission facility. The use of the distributed repeaters is cost-efficient and can increase frequency utility efficiency.
FIG. 3 illustrates an example of a service employing conventional distributed repeaters. A main transmitter 301 sends out broadcasting signals through a transmission frequency A, and distributed repeaters 302 to 305 repeat the broadcasting signals through a frequency B that is different from the transmission frequency A.
When a network is configured using on-channel repeaters or distributed repeaters, frequency utility efficiency may be increased because frequency can be reused. However, there is a problem that interference occurs on adjacent repeaters because a single frequency is used between a transmitter and a repeater or between repeaters. To resolve the problem, an identification (ID) signal with an excellent correlation characteristic is assigned to the transmitter and the repeaters, adds the ID signal to the broadcasting signals, and transmits the broadcasting signals. Desired signals can be detected using an ID signal analyzing apparatus, in spite of interference caused by other signals.
Herein, since a sequence used as the ID signal is embedded to broadcasting signal in the form of spread spectrum to minimize the influence of existing service signals, a high bit resolution is required to represent the ID signals. Also, a long sequence is used as the ID signal to acquire excellent correlation characteristic. For example, in the Advanced Television System Committee (ATSC) system, which is the digital broadcasting system of the United States, a Kasami sequence having a length of 64896 is used as an ID signal, and it is added 21 to 39 dB smaller than the signal power of the main broadcasting service signals. An ID signal analyzing apparatus requires a much computation amount to detect and analyze an ID signal. In short, the ID signal analyzing apparatus requires high complexity.
Therefore, it is desperately needed to develop an ID signal analyzing apparatus having a low complexity to analyze an ID signal having high bit resolution and long length.